Temperature-dependent interlayer coupling in Ni/Co perpendicular pseudo-spin-valve structures

Abstract

The temperature-dependent coupling mechanisms in perpendicular pseudo-spin valves based on the following structure, [Ni/Co]${}_{5}$/Cu(t${}_{\mathrm{Cu}}$)/[Ni/Co]${}_{2}$, are investigated. Despite a thick (t${}_{\mathrm{Cu}}\ensuremath{\ge}3$ nm) Cu spacer, room-temperature measurements reveal complete coupling of the [Ni/Co]${}_{5}$ and [Ni/Co]${}_{2}$ multilayers. This coupling can be attributed to strong long range magnetostatic stray fields that penetrate the spacer layer. This results in magnetic domain imprinting and vertically correlated domains throughout the reversal process. Surprisingly, when the temperature is reduced, a complete decoupling is observed. This somewhat counterintuitive result can be explained by a large difference in the [Ni/Co]${}_{5}$ and [Ni/Co]${}_{2}$ multilayer coercivities at reduced temperatures, which then impedes domain imprinting and promotes decoupling. Finally, the decoupling temperature is found to increase with spacer thickness.